Spray 13x9-inch (3-quart) glass baking dish with cooking spray. In 12-inch skillet, cook sausage over medium heat 8 to 10 minutes, stirring occasionally, until no longer pink; drain.
Spread half of the diced muffins in pan; top with half of the sausage, half of the onions and half of the cranberries. Repeat layers with remaining muffins, sausage, onions and cranberries.
In large bowl, beat eggs, milk, sour cream, salt and pepper with wire whisk until well blended; pour over mixture in pan. Sprinkle cheese over top. Spray sheet of foil with cooking spray; place sprayed side down over pan. Cover; refrigerate at least 4 hours but no longer than 24 hours.
Heat oven to 325°F Bake covered 30 minutes. Uncover; bake 30 to 40 minutes longer or until top is golden brown and knife inserted in center comes out clean. Cut into squares.